Semiconductor device

ABSTRACT

With this semiconductor device, the distortion and cracking of a thinned portion of a semiconductor substrate are prevented to enable high precision focusing with respect to a photodetecting unit and uniformity and stability of high sensitivity of the photodetecting unit to be maintained. A semiconductor device  1  has a semiconductor substrate  10,  a wiring substrate  20,  conductive bumps  30,  and a resin  32.  A CCD  12  and a thinned portion  14  are formed on semiconductor substrate  10.  Electrodes  16  of semiconductor substrate  10  are connected via conductive bumps  30  to electrodes  22  of wiring substrate  20.  Wiring substrate  20  has formed therein a groove portion  26   a  that surrounds a region opposing thinned portion  14  and groove portions  26   b  that extend to an exposed surface of wiring substrate  20  from groove portion  26   a . Insulating resin  32  fills a gap between outer edge  15  of thinned portion  14  and wiring substrate  20  to reinforce the bonding strengths of conductive bumps  30.

TECHNICAL FIELD

This invention concerns a semiconductor device and particularly concernsa back-illuminated semiconductor device.

BACKGROUND ART

A so-called back-illuminated semiconductor photodetecting device hasbeen known conventionally as a semiconductor device. This type ofsemiconductor device has a semiconductor substrate and has aphotodetecting unit on one surface of the semiconductor substrate. Aportion of the semiconductor substrate on the side opposite thephotodetecting unit is trimmed to form a recessed portion in thesemiconductor substrate. A thinned portion is thus provided at theportion of the semiconductor substrate at which the photodetecting unitis disposed. This thinned portion is provided to accommodate ultravioletrays, soft X-rays, electronic beams, and other energy rays that will beabsorbed and cannot be detected at high sensitivity by a thicksemiconductor substrate. At this thinned portion, light that is madeincident on the surface at the recessed portion side of thesemiconductor substrate is detected by the photodetecting unit.

As an example of a back-illuminated semiconductor device, there is asemiconductor device that has a BT-CCD (back-thinned CCD). The BT-CCD isused as a detecting unit of a semiconductor inspecting device. Anexample of a conventional semiconductor device having a BT-CCD isdescribed in Patent Document 1.

FIG. 8 is a sectional view of an arrangement of the semiconductor devicedescribed in Patent Document 1. As shown in FIG. 8, a P-type siliconlayer 104, which is a semiconductor substrate having a CCD 103 on asurface that opposes a wiring substrate 102, is mounted via metal bumps105 onto wiring substrate 102, which is fixed to a bottom portion of theinterior of a package 101. Each wiring 106 on wiring substrate 102 isconnected at one end to a metal bump 105 and has a bonding pad (notshown) for externally taking out detected signals at the other end, andeach bonding pad is electrically connected by a bonding wire 107 to alead terminal (not shown) of package 101. Furthermore, a gap betweenwiring substrate 102 and P-type silicon layer 104 is filled with anunderfill resin 108 for reinforcing the bonding strengths of metal bumps105.

Patent Document 1: Japanese Published Unexamined Patent Application No.Hei 6-196680

However, when the underfill resin fills the gap between the wiringsubstrate and the thinned portion of the semiconductor substrate asshown in FIG. 8, the thinned portion may crack due to the stress thatarises due to a thermal expansion coefficient difference between theunderfill resin and the semiconductor substrate in the process ofheating or cooling to cure the underfill resin. Even if cracking doesnot occur, the thinned portion may become distorted by being pulled bythe contraction of the underfill resin. Such distortion of the thinnedportion of the semiconductor substrate may bring about adverse effectson focusing with respect to the photodetecting unit and uniformity andstability of sensitivity of the photodetecting unit during use of thesemiconductor device.

This invention was made in view of the above issue and an object thereofis to provide a semiconductor device, with which the distortion andcracking of a thinned portion of a semiconductor substrate are preventedto enable high precision focusing with respect to a photodetecting unitand uniformity and stability of high sensitivity of the photodetectingunit to be maintained.

DISCLOSURE OF THE INVENTION

In order to solve the above issue, this invention provides asemiconductor device, comprising: a semiconductor substrate, having aphotodetecting unit formed on one surface, a thinned portion formed byetching a region, opposing the photodetecting unit, of another surface,and first electrodes disposed on the one surface at an outer edge of thethinned portion and electrically connected to the photodetecting unit; awiring substrate, disposed to oppose the one surface side of thesemiconductor substrate and having second electrodes connected viaconductive bumps to the first electrodes; and a resin, filling a gapbetween the wiring substrate and the outer edge of the thinned portionto reinforce the strengths of bonding of the respective first electrodesand the respective second electrodes with the conductive bumps; andbeing characterized in that the wiring substrate has formed therein agroove portion that surrounds a region opposing the thinned portion andcommunicating portions that extend from the groove portion to an exposedsurface of the wiring substrate.

With this semiconductor device, the resin fills the gap between thewiring substrate and the outer edge of the thinned portion. The strengthof bonding of the conductive bumps with the first electrodes that aredisposed at the outer edge of the thinned portion and the strength ofbonding of the conductive bumps with the second electrodes of the wiringsubstrate are thus reinforced. Meanwhile, because the resin does notfill a gap between the wiring substrate and the thinned portion of thesemiconductor substrate, even when stress due to the thermal expansioncoefficient difference between the resin and the semiconductor substratearises during heating or cooling in the process of curing the resin,etc., the influence of the stress on the thinned portion will be smalland distortion and cracking of the thinned portion will be prevented.Thus with this semiconductor device, high precision focusing is enabledwith respect to the photodetecting unit and uniformity and stability ofhigh sensitivity of the photodetecting unit can be exhibited during use.

Furthermore, the wiring substrate has a groove portion formed therein soas to surround the region opposing the thinned portion. Thus, forexample, in the process of filling the gap between the semiconductorsubstrate and the wiring substrate with the resin using the capillaryphenomenon during manufacture of the semiconductor device, when theresin entering into the gap from a periphery of the semiconductorsubstrate reaches the groove portion, the capillary phenomenon does notproceed any further and the entry of the resin stops. By such a grooveportion being provided in the wiring substrate, an arrangement, whereinthe resin fills the gap at which the conductive bumps exist, that is,the gap between the wiring substrate and the outer edge of the thinnedportion while the gap between the wiring substrate and the thinnedportion at the inner side of the groove portion is left unfilled, can bereadily realized.

With this semiconductor device, the gap between the thinned portion andthe wiring substrate may become completely surrounded by the resin thatfills the gap between the outer edge of the thinned portion and thewiring substrate. In this case, if the surrounded gap becomes sealed,the thinned portion may become distorted due to expansion or contractionof the air inside the sealed space during heating or cooling in theprocess of curing the resin, etc. In regard to this issue, with thepresent semiconductor device, the communicating portions that extendfrom the groove portion to the exposed surface of the wiring substrateare provided so that air can move freely between the gap surrounded bythe resin and the exterior of the semiconductor device via thecommunicating portions, and the gap surrounded by the resin is therebyprevented from becoming sealed.

An “exposed surface of the wiring substrate” refers to a region of theupper surface (surface opposing the semiconductor substrate) of thewiring substrate that is located at the outer side of the region coveredby the above-mentioned resin as well as to a bottom surface and a sidesurface of the wiring substrate.

The communicating portions are preferably second groove portions thatare formed in the surface of the wiring substrate that opposes thesemiconductor substrate. In this case, since the groove portion and thecommunicating portions (second groove portions) can be formed in thesame process, the manufacture of the wiring substrate and thus thesemiconductor as a whole is facilitated.

The communicating portions are preferably through-holes that passthrough the wiring substrate. In this case, even if the entire gapbetween the outer edge of the thinned portion of the semiconductorsubstrate and the wiring substrate is filled with the resin, the sealingof the gap between the thinned portion and the wiring substrate can beprevented by the through-holes and thus the mechanical strength of thesemiconductor substrate can be improved further.

The photodetecting unit may have a plurality of pixels that are arrayedone-dimensionally or two-dimensionally. This invention's semiconductordevice is especially useful in this case because uniformity andstability of high sensitivity is required among the plurality of pixels.

Also preferably, the wiring substrate has first lead terminals, to whichsignals that drive the photodetecting unit are provided, and second leadterminals that output detected signals from the photodetecting unit, andamong the plurality of second electrodes, those that are connected tothe second lead terminals are positioned inside the region surrounded bythe groove portion, and among the plurality of second electrodes, thosethat are connected to the first lead terminals are positioned outsidethe region surrounded by the groove portion. In this case, since theelectrodes that provide the driving signals and the electrodes forreading signals are positioned in a physically separated manner acrossthe groove portion as a boundary, crosstalk can be restrained.

A gas (air) is interposed between the thinned portion of thesemiconductor substrate and the wiring substrate. As this gas, an inertgas, such as nitrogen or argon is preferable, and distortions of bothsubstrates can thereby be tolerated and degradation of the innersurfaces of the substrates can be restrained.

By this invention, a semiconductor device can be realized with which thedistortion and cracking of a thinned portion of a semiconductorsubstrate are prevented to enable high precision focusing with respectto a photodetecting unit and uniformity and stability of highsensitivity of the photodetecting unit to be maintained.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of an embodiment of this invention'ssemiconductor device;

FIG. 2 is a plan view for describing an arrangement of a groove portion26 of FIG. 1;

FIG. 3 is a sectional view of another embodiment of this invention'ssemiconductor device;

FIG. 4 is a plan view for describing structures of a groove portion 27 aand a through-holes 27 b of FIG. 3;

FIG. 5 is a plan view of an arrangement example of wiring substrate 20of FIG. 1;

FIG. 6 is a sectional view of an arrangement of internal wirings ofwiring substrate 20 of the arrangement example of FIG. 5;

FIG. 7 is a sectional view for describing the arrangement of internalwirings 60 of FIG. 6; and

FIG. 8 is a sectional view of an arrangement of a conventionalsemiconductor device.

Explanation of Reference Numerals  1, 2 semiconductor device 10semiconductor substrate 14 thinned portion 15 outer edge 16 electrode 18accumulation layer 20, 21 wiring substrate 22 electrode 24 lead terminal26a, 27a groove portion 26b groove portion (communicating portion) 27bthrough-hole (communicating portion) 28 chip resistor 30 conductive bump32 resin

BEST MODES FOR CARRYING OUT THE INVENTION

Preferred embodiments of this invention's semiconductor device shall nowbe described in detail along with the drawings. In the description ofthe drawings, the same elements shall be provided with the same symbolsand overlapping description shall be omitted. The dimensionalproportions in the drawings do not necessary match those of thedescription.

FIG. 1 is a sectional view of an embodiment of this invention'ssemiconductor device. A semiconductor device 1 has a semiconductorsubstrate 10, a wiring substrate 20, conductive bumps 30, and a resin32. Semiconductor substrate 10 is a BT-CCD (back-thinned CCD) and has aCCD 12 formed as a photodetecting unit on a portion of a top layer ofits front surface S1 side. Semiconductor substrate 10 includes, forexample, a silicon P⁺ layer, a P-type epitaxial layer formed above thesilicon P⁺ layer, and an unillustrated set of transfer electrodes formedon the epitaxial layer. CCD 12 has a plurality of pixels that arearrayed two-dimensionally. Also, a thinned portion 14 is formed bythinning by etching a region, opposing CCD 12, of a back surface S2. Theetched portion has a truncated rectangular pyramidal profile. A surfaceof thinned portion 14 at the etched side is a flat and rectangular,light-incident surface S3, and this light-incident surface S3 is formedto be substantially the same in size as CCD 12. Semiconductor substrate10 as a whole has a rectangular shape in plan view. Semiconductorsubstrate 10 is, for example, approximately 15 to 40 μm thick at thinnedportion 14 and approximately 300 to 600 μm thick at an outer edge 15 ofthinned portion 14. Outer edge 15 of thinned portion 14 refers to aportion of semiconductor substrate at the periphery of thinned portion14 and is thicker than thinned portion 14.

Electrodes 16 (first electrodes) are formed on front surface S1 of outeredge 15. These electrodes 16 are electrically connected to the set oftransfer electrodes of CCD 12 by wirings that are omitted fromillustration. The entirety of back surface S2 of semiconductor substrate10, including light-incident surface S3, is covered by an accumulationlayer 18. Accumulation layer 18 is of the same conductive type assemiconductor substrate 10, however, is higher in impurity concentrationthan semiconductor substrate 10.

Semiconductor substrate 10 is mounted onto wiring substrate 20 byflip-chip bonding. Wiring substrate 20 is thus positioned to oppose thefront surface S1 side of semiconductor substrate 10. Electrodes 22(second electrodes) are formed at positions of wiring substrate 20 thatoppose electrodes 16 of semiconductor substrate 10, and these electrodes22 are connected via conductive bumps 30 to electrodes 16. Leadterminals 24, electrodes 22, conductive bumps 30, and electrodes 16 arethus connected to the CCD transfer electrodes and CCD driving signalsare input into lead terminals 24. An output of an amplifier that outputsa CCD read signal is taken out from a lead terminal 24 via an electrode16, a conductive bump 30, and an electrode 22. Wiring substrate 20 isformed, for example, of a multilayer ceramic substrate. An upper surfaceS4 (surface opposing semiconductor substrate 10) of wiring substrate 20has a wider area than semiconductor substrate 10 and a region that doesnot oppose semiconductor substrate exists at an edge of upper surfaceS4.

Due to the interposition of conductive bumps 30, a gap exists betweensemiconductor substrate 10 and wiring substrate 20. Of this gap, aportion that is sandwiched by outer edge 15 and wiring substrate 20 isfilled with insulating resin 32 (underfill resin) for reinforcing thebonding strengths of conductive bumps 30 (specifically the strengths ofbonding of conductive bumps 30 with the respective electrodes 16 andelectrodes 22). As resin 32, for example, an epoxy-based resin, aurethane-based resin, a silicone-based resin, an acrylic-based resin, ora composite of such resins is used.

Lead terminals 24 are disposed at a bottom surface S5 (surface at theopposite side of upper surface S4) of wiring substrate 20. Leadterminals 24 are connected to internal wirings (not shown) of wiringsubstrate 20.

A groove portion 26 is formed in upper surface S4 of wiring substrate20. An arrangement of groove portion 26 shall now be described usingFIG. 2. FIG. 2 is a plan view of wiring substrate 20 as viewed from itsupper surface S4 side. In FIG. 2, broken lines L1 and L2 indicateoutlines of semiconductor substrate 10 and thinned portion 14,respectively. The sectional view taken on line I-I of this figurecorresponds to being FIG. 1. As shown in FIG. 2, groove portion 26includes a groove portion 26 a (first groove portion) and grooveportions 26 b (second groove portions). Groove portions 26 a and 26 bare formed in upper surface S4 of wiring substrate 20 and extend alongdirections within the plane of the surface.

Groove portion 26 a is formed along a periphery of a region (regionsurrounded by broken lines L2) of wiring substrate 20 that opposesthinned portion 14 of semiconductor substrate 10 and surrounds theregion that opposes thinned portion 14. On wiring substrate 20, grooveportion 26 a has a rectangular shape as a whole. Meanwhile, a total offour groove portions 26 b are formed, and one end E1 of each grooveportion 26 b is connected to one of the four corners of groove portion26 a. Another end E2 of each groove portion 26 b is exposed at the outerside of a region (region surrounded by broken lines L1) of wiringsubstrate 20 that opposes semiconductor substrate 10. Each of grooveportions 26 b thus extends from groove portion 26 a to an exposedsurface of wiring substrate 20. Groove portions 26 b thus function ascommunicating portions that put groove portion 26 a and the exterior ofsemiconductor device 1 in communication.

An exposed surface of wiring substrate 20 refers to a surface, among thesurfaces of wiring substrate 20, that is exposed to the exterior ofsemiconductor device 1. The region of the upper surface S4 of wiringsubstrate 20 that is positioned at the outer side of the region coveredwith resin 32, bottom surface S5 and side surfaces S6 of wiringsubstrate 20 (see FIG. 1) correspond to being exposed surfaces. Thusalthough the region of wiring substrate 20 that opposes thinned portion14 is not covered with resin 32, since it is located at the inner sideof the region covered by resin 32 as shown in FIG. 1, this region doesnot correspond to being an exposed surface.

In FIG. 2, the portions of the gap between semiconductor substrate 10and wiring substrate 20 that are filled with resin 32 are indicated byslanted lines. As shown in this figure, in this embodiment, resin 32fills only the portions of the above-mentioned gap at the outer side ofgroove portion 26 a and does not fill portion 26 a and portions at theinner side thereof. Portions at the outer side of groove portion 26 a atwhich groove portions 26 b are formed are also not filled with resin 32.

Furthermore, a plurality of chip resistors 28 are disposed on uppersurface S4 of wiring substrate 20. Chip resistors 28 are alignedone-dimensionally in the left/right direction of the figure,respectively at an upper portion and a lower portion in the figure ofthe region of wiring substrate 20 that is surrounded by groove portion26 a.

Returning now to FIG. 1, operations of semiconductor device 1 shall bedescribed. Light made incident on thinned portion 14 of semiconductorsubstrate 10 from light-incident surface S3 is detected by CCD 12. Thedetected signals pass through electrodes 16, conductive bumps 30,electrodes 22, in that order, and are thereby transmitted to wiringsubstrate 20. The detected signals (CCD read signals) are thentransmitted to lead terminals 24 and output from lead terminals 24 tothe exterior of semiconductor device 1.

The effects of semiconductor device 1 shall now be described. Resin 32fills the gap between outer edge 15 of thinned portion 14 and wiringsubstrate 20. The strength of bonding of electrodes 16, disposed onouter edge 15 of thinned portion 14, with conductive bumps 30 and thestrength of bonding of conductive bumps 30 with electrodes 22 of wiringsubstrate 20 are thereby reinforced. Meanwhile, because the gap betweenthinned portion 14 of semiconductor substrate 10 and wiring substrate 20is not filled with resin 32, even if stress due to the thermal expansioncoefficient difference between resin 32 and semiconductor substrate 10arises between the two during heating or cooling in the process ofcuring resin 32, etc., the influence of the stress on thinned portion 14will be low and distortion and cracking of thinned portion 14 areprevented. Thus with semiconductor device 1, high precision focusingwith respect to CCD 12 is enabled and uniformity and stability of thehigh sensitivity of CCD 12 can be exhibited during use. Also, becausecracking of thinned portion 14 is prevented, the manufacturing yield ofsemiconductor device 1 is improved.

Furthermore, wiring substrate 20 has groove portion 26 a formed thereinso as to surround the region opposing thinned portion 14. Thus, forexample, in the process of filling the gap between semiconductorsubstrate 10 and wiring substrate 20 with the resin using the capillaryphenomenon during manufacture of semiconductor device 1, when the resinentering into the gap from the periphery of semiconductor substrate 10reaches groove portion 26 a, the capillary phenomenon does not proceedany further and the entry of the resin stops. By such a groove portion26 a being provided in wiring substrate 20, the arrangement, whereinresin 32 fills the gap at which conductive bumps 30 exist, that is, thegap between wiring substrate 20 and outer edge 15 of thinned portion 14while the gap between wiring substrate 20 and thinned portion 14 at theinner side of groove portion 26 a is left unfilled, can be readilyrealized.

With semiconductor device 1, the gap between thinned portion 14 andwiring substrate 20 may become completely surrounded by resin 32 thatfills the gap between outer edge 15 of thinned portion 14 and wiringsubstrate 20. In this case, if the surrounded gap becomes sealed,thinned portion 14 may become distorted due to expansion or contractionof the air inside the sealed space during heating or cooling in theprocess of curing the resin, etc. In regard to this issue, withsemiconductor device 1, groove portions 26 b that extend from grooveportion 26 a to the exposed surface of wiring substrate 20 are providedso that air can move freely between the gap surrounded by resin 32 andthe exterior of semiconductor device 1 via groove portions 26 b, and thegap surrounded by resin 32 is thereby prevented from becoming sealed.

A gas (air) is interposed between thinned portion 14 of thesemiconductor substrate and wiring substrate 20. As this gas, an inertgas, such as nitrogen or argon is preferable, and distortions of bothsubstrates can thereby be tolerated and degradation of the innersurfaces of the substrates can be restrained.

As with groove portion 26 a, groove portions 26 b are formed in thesurface of wiring substrate 20 that opposes semiconductor substrate 10.In this case, since both groove portions 26 a and 26 b can be formed inthe same process, the manufacture of wiring substrate 20 and thus ofsemiconductor device 1 as a whole is facilitated.

Semiconductor substrate 10 is provided with accumulation layer 18. Theaccumulation state of semiconductor substrate 10 is thereby maintained.Thereby the uniformity and stability of the sensitivity of CCD 12 withrespect to short wavelength light can be improved further.

In recent years, demands for large area and high-speed responsecharacteristics have been increasing for back-illuminated semiconductordevices. However, with an arrangement, such as that of the semiconductordevice shown in FIG. 8, wherein the semiconductor substrate is diebonded once to the wiring substrate and then the wiring substrate iswire bonded to the lead terminals of the package, it is difficult torealize a large area and a high-speed response at the same time. Thatis, when the semiconductor device of this arrangement is made large inarea, the resistance increases due to the accompanying elongation of thewires. Moreover, because in accordance with the making of the arealarge, the occurrence of crosstalk, the forming of capacitance(capacitor) between the wires, and other issues arise due to wiresbecoming close to each other and high in density, the realization ofhigh-speed response is made even more difficult.

Meanwhile, with semiconductor device 1, because semiconductor substrate10 is mounted onto wiring substrate 20 via conductive bumps 30, there isno need to perform wire bonding of semiconductor substrate 10 withwiring substrate 20. Furthermore, because wiring substrate 20 isprovided with lead terminals 24, there is no need to provide a packagebesides wiring substrate 20 and thus, with semiconductor device 1, thereis no need to perform wire bonding of wiring substrate 20 with leadterminals of a package. Thus with semiconductor device 1, because all ofthe wirings can be arranged without using wire bonding, even if a largearea is to be realized, the above-mentioned problems of increasedresistance, occurrence of crosstalk, and forming of capacitance do notoccur. Semiconductor device 1 can thus meet the demands of both largearea and high-speed response. For example, when the number of pixels ofCCD 12 is 2054 pixels×1024 pixels (with the chip size (area ofsemiconductor substrate 10) being slightly over 40.0 mm×20 mm), whereasspeeding up of the response to a rate of 1.6 Gpixels/sec or more isdifficult with the conventional semiconductor device, high-speedoperation at 3.2 Gpixels/sec is enabled with semiconductor device 1.

FIG. 3 is a sectional view of another embodiment of this invention'ssemiconductor device. A semiconductor device 2 has semiconductorsubstrate 10, a wiring substrate 21, conductive bumps 30, and resin 32.With semiconductor device 2, the structure of wiring substrate 21differs from that of wiring substrate 20 of semiconductor device 1 shownin FIG. 1. Because the rest of arrangements are the same as those ofsemiconductor device 1 of FIG. 1, description thereof shall be omitted.Wiring substrate 21 has a groove portion 27 a and through-holes 27 bformed therein. As with groove portion 26 a of semiconductor device 1,groove portion 27 a is formed along the periphery of the region of thewiring substrate 21 that opposes thinned portion 14. With eachthrough-hole 27 b, one end is connected to groove portion 27 a and theother end is exposed at bottom surface S5 of wiring substrate 21. Thatis, through-holes 27 b pass through wiring substrate 21 and extend fromgroove portion 27 a to bottom surface S5. Through-holes 27 b thusfunction as communicating portions that put groove portion 27 a and theexterior of semiconductor device 2 in communication.

The structures of groove portion 27 a and through-holes 27 b shall nowbe described in more detail using FIG. 4. FIG. 4 is a plan view ofwiring substrate 21 as viewed from its upper surface S4 side. As shownin this figure, through-holes 27 b have cylindrical shapes and arerespectively formed at and connected to the four corners of grooveportion 27 a. With this embodiment, in accordance with communicatingportions (through-holes 27 b) not being formed on upper surface S4 ofwiring substrate 21, the entirety of the portion of the gap betweensemiconductor substrate 10 and wiring substrate 21 that lies to theouter side of groove portion 27 a (the portion provided with slantedlines in FIG. 4) is filled with resin 32.

With semiconductor device 2 of the above arrangement, distortion andcracking of thinned portion 14 are prevented as with semiconductordevice 1, and thus high precision focusing with respect to CCD 12 isenabled and uniformity and stability of the high sensitivity of CCD 12can be exhibited during use. Furthermore, by groove portion 27 a beingformed in wiring substrate 21, the arrangement, wherein resin 32 fillsthe gap between wiring substrate 21 and outer edge 15 of thinned portion14 while the gap between wiring substrate 21 and thinned portion 14 isleft unfilled, can be readily realized. Groove portions, which are thesame communicating portions as groove portions 26 b described above,extend from the four corners of the rectangular groove portion 27 a tothe four corners of wiring substrate 21, and through-holes 27 b areformed at the positions at which the groove portions are connected. Bythrough-holes 27 b being formed in wiring substrate 21, the gap betweenthinned portion 14 and wiring substrate 21 can be prevented from beingsealed, and the distortion of thinned portion 14 due to expansion orcontraction of air in a sealed space can thus be prevented.

Through-holes 27 b are provided as communicating portions that put thegap between thinned portion 14 and wiring substrate 21 in communicationwith the exterior of semiconductor device 2. Since the sealing of thegap between thinned portion 14 and wiring substrate 21 can thus beprevented by through-holes 27 b even when the entirety of the gapbetween outer edge 15 of thinned portion 14 and wiring substrate 21 isfilled with resin 32, the mechanical strength of semiconductor device 2can be further improved.

FIG. 5 is a plan view of an arrangement example of wiring substrate 20of FIG. 1. Wiring substrate 20 of this arrangement example is amultilayer ceramic substrate. This wiring substrate 20 has asubstantially square shape of 58.420 mm square in plan view and hasgroove portion 26 a, which defines a rectangle of 38.700 mm×18.900 mm,formed in a central portion thereof. Also, groove portions 26 b areformed so as to be respectively connected to the four corners of grooveportion 26 a. The plurality of chip resistors 28 are disposed in therectangular region surrounded by groove portion 26 a. In this region,chip resistors 28 are aligned one-dimensionally in the left/rightdirection of the figure (in the direction of the long sides of theabove-mentioned rectangle) in two columns at each of an upper portionand a lower portion in the figure. The plurality of electrodes 22 areformed in a region at the outer side of groove portion 26 a. Electrodes22 are aligned along each of the four sides of the above-mentionedrectangle, forming three columns along each of the long sides andforming two columns along each of the short sides. The diameter of eachelectrode 22 is 0.080 mm.

FIG. 6 is a sectional view of an arrangement of internal wirings ofwiring substrate 20 of the arrangement example of FIG. 5.

Internal wirings 60 include signal output wirings 60 a and 60 b, clocksupplying wirings 60 c and 60 d, and DC bias (ground) supplying wirings60 e. Each internal wiring 60 electrically connects an electrode 22, alead terminal 24, and a chip resistor 28 to each other. The arrangementof internal wirings 60 shall now be described in more detail using FIG.7. In FIG. 7, a plurality of lead terminals 24 are indicatedoverlappingly on a plan view of wiring substrate 20 for the sake ofdescription. As shown in this figure, whereas only signal output wirings60 a and 60 b are formed at portions to the inner side of groove portion26 a, clock supplying wirings 60 c and 60 d and DC bias (clock)supplying wiring 60 e are formed at portions to the outer side of grooveportion 26 a. By thus positioning the driving system wirings of clocksupplying wirings 60 c and 60 d and DC bias supplying wiring 60 eseparately from signal output wirings 60 a and 60 b, the occurrence ofcrosstalk between the driving system signals and the output systemsignals can be prevented.

That is, on the wiring substrate are disposed first lead terminals 24,to which are provided signals for driving the photodetecting unit, andsecond lead terminals (24; indicated by the same symbol) for outputtingdetected signals from the photodetecting unit, and among the pluralityof second electrodes 22, those that are connected to the second leadterminals (24) are positioned inside the region surrounded by grooveportion 26 a, and among the plurality of second electrodes 22, thosethat are connected to the first lead terminals (24) are positionedoutside the region surrounded by groove portion 26 a. In this case,since second electrodes 22 that provide the driving signals (clock) andsecond electrodes 22 for reading signals (outputting signals) arepositioned in a physically separated manner across groove portion 26 aas a boundary, crosstalk can be restrained.

This invention's semiconductor device is not restricted to theembodiment described above and various modifications are possible. Forexample, although an arrangement, wherein the other ends of thecommunicating portions (groove portions 26 b) are exposed at the outerside of the region of wiring substrate 20 that opposes semiconductorsubstrate 10, was shown in FIG. 2 and an arrangement, wherein the otherends of the communicating portions (through-holes 27 b) are exposed atbottom surface S5, was shown in FIG. 3, the other ends of thecommunicating portions may instead be exposed at side surfaces S6 ofwiring substrate 20 or 21.

Also, although arrangements, in each of which groove portion 26 a or 27a completely surrounds the region of wiring substrate 20 or 21 thatopposes thinned portion 14, were described, an arrangement, whereingroove portion 26 a or 27 a surrounds the above-mentioned region exceptat portions of the periphery of the region, is also possible.

Also, although arrangements, in each of which four groove portions 26 band four through-holes 27 b are respectively formed in wiring substrate20 and 21, were described, an arrangement, wherein just one of thegroove portions or one of the through-holes is formed, is possible as isan arrangement, wherein two or more of the groove portions or thethrough-holes are formed.

INDUSTRIAL APPLICABILITY

This invention concerns a semiconductor device and can be usedespecially in a back-illuminated semiconductor device.

1. A back-illuminated semiconductor device comprising: a semiconductorsubstrate, having: a photodetecting unit formed on one surface, a recessformed by etching a region, opposing the photodetecting unit, of anothersurface, wherein the recess is formed at light incident side of thesemiconductor substrate, an outer edge surrounding the recess, and firstelectrodes disposed on the one surface at the outer edge andelectrically connected to the photodetecting unit; a wiring substrate,disposed to oppose the one surface side of the semiconductor substrateand having second electrodes connected via conductive bumps to the firstelectrodes; and a resin, filling a gap between the wiring substrate andthe outer edge with the conductive bumps; wherein the wiring substratehas formed therein a groove portion that surrounds a region opposing therecess and communicating portions that extend from the groove portion toan exposed surface of the wiring substrate, wherein the exposed surfaceof the wiring substrate is located at an outer side of a region coveredby the resin.
 2. The semiconductor device according to claim 1, whereinthe communicating portions are second groove portions formed on asurface of the wiring substrate that opposes the semiconductorsubstrate.
 3. The semiconductor device according to claim 1, wherein thecommunicating portions are through-holes that pass through the wiringsubstrate.
 4. The semiconductor device according to any of claims 1through 3, wherein the photodetecting unit has a plurality of pixelsthat are arrayed one-dimensionally or two-dimensionally.
 5. Thesemiconductor device according to claim 1, wherein the wiring substratehas first lead terminals, to which signals that drive the photodetectingunit are provided, and second lead terminals that output detectedsignals from the photodetecting unit, and among the plurality of secondelectrodes, those that are connected to the second lead terminals arepositioned inside the region surrounded by the groove portion, among theplurality of second electrodes, those that are connected to the firstlead terminals are positioned outside the region surrounded by thegroove portion.
 6. The semiconductor device according to claim 1,wherein a gas is interposed between the recess of the semiconductorsubstrate and the wiring substrate.